Lubrication tests have indicated that a glycoprotein (LGP-I) is the component which enables synovial fluid to act as a boundary lubricant for articular cartilage. Chemical studies will be carried out to determine the peptide structures of LGP-I, and whether this molecule contains one or two types of carbohydrate side chains. In addition electron microscope, light scattering and enzymic studies will be carried out to relate molecular structure to its ability to act as a lubricant. Studies carried out on the structure of articular cartilage have shown that this tissue contains a complex mixture of different types of proteoglycans and glycoproteins. Experiments will be carried out to determine which articular cartilage components interact with LGP-I and thus may act as receptors for LGP-I enabling it to act as a boundary lubricant.